1. Field of the Invention
The present invention relates to a bone-conduction microphone built-in headset that collects sounds emitted from a person through bones of his or her body.
2. Description of the Related Art
Microphones applying bone conduction are used in cell phones, medical field, arms industry, and other various fields. A person usually senses a sound when vibratory pressure of air caused by a sound source vibrates an eardrum in his or her middle ear and the vibration is sent as a signal to the brain via an auditory nervous system and the like related to a sense of hearing. The sound thus sensed is referred to as an air-conduction sound.
Meanwhile, the bone conduction allows a person to sense a sound by vibrating apart of his or her skull with an oscillator in contact with his or her head. The sound thus sensed is referred to as a bone-conduction sound. As can be seen, the bone-conduction sound is transmitted in a different way from the air-conduction sound. Microphones and speakers applying bone conduction are advantageously used by a user who has difficulty hearing sounds because: the user is surrounded by noise; or a part of a user's organ of hearing sense, such as an eardrum, is impaired.
The user uses conventional bone-conduction microphones to communicate without being affected by the surrounding noise as much as possible by, for example: fixing a bone-conduction microphone unit at a user's throat with a neckband or an arm; or fixing the bone-conduction microphone unit to a tip of a headband or a headset or a tip of an arm connected to the tip of the headband or the headset and pressing the bone-conduction microphone unit to a user's cheek bone or temple with lateral pressure or with a user's hand.
As described above, the conventional bone-conduction microphone requires special arm, neckband, or headband to press the bone-conduction microphone unit against a part of a user's body at which a sound can be conducted efficiently. Thus, the bone-conduction microphone is usually troublesome and cumbersome upon wearing. Moreover, even when used together with a headphone and the like, the user has to take trouble of setting the head phone and the bone-conduction microphone separately.
Further, clear communication is difficult with the bone-conduction microphone mounted on the tip of the headband, the neckband, or the arm because the headband, the neckband, and the arm fixing the position of the bone-conduction microphone are vibrated by the surrounding noise and the noise is transferred to the bone-conduction microphone unit. A bone-conduction microphone is available in which the bone-conduction microphone unit is acoustically separated from the headband and the arm by interposing a rubber and the like. However, this type of bone-conduction microphone requires the user to manually place the microphone unit near a user's mouth. Therefore, fine sound quality can be obtained by using this type of bone-conduction microphone. However, the user cannot use a user's hand for any other purpose, because the user holds this type of bone-conduction microphone with the user's hand.
A wireless communication device comprising a wireless transceiver device, a headset, and a bone-conduction microphone is used for communication under huge noise. Because each of the elements are formed separately and connected via a connection cord and the like, operability and workability of the wireless communication device become low and wearing and removing the headset and the bone-conduction microphone become cumbersome.
As a solution to the problem, Japanese Unexamined Utility Model Application Publication No. 7-1629 discloses an integrated structure in which a headset incorporates a wireless transceiver circuit board, a speaker, and a bone-conduction microphone while an antenna wire is fixed along a headband thereof. Here, by employing a interactive communication or a voice operated transmission (VOX) circuit for the wireless transceiver circuit board, workability and operability for the user can be enhanced.
With the invention disclosed in the Japanese Unexamined Utility Model Application Publication No. 7-1629, a frequency characteristic of the bone-conduction microphone can be controlled so that the person on the other end of the line would not notice the surrounding noise transferred from the headband, neckband, or the arm because the interactive communication or the VOX circuit is used for the wireless transceiver circuit. Unfortunately, the technique provides a bone-conduction microphone with a lower performance and thus, adequacy as a communication tool is questionable. Moreover, the interactive communication or the VOX circuit degrades functionality of the bone-conduction microphone and thus, regardless of the surrounding noise, the voice cannot be clearly sent to the person on the other end of the line.